1. Field of the Invention
This invention relates generally to the field of biomarker detection. More particularly, it relates to peptides against neuropeptide Y and methods of using the same.
2. Description of the Related Art
Biomarkers are present in a variety of easily-accessible bodily fluids, including saliva, sweat, blood, and urine, and may be used to predict, identify, and monitor medical disorders and diseases ranging from mental disorders such as schizophrenia to cancer and bacterial and viral infections. Neuropeptide Y (NPY) is a highly abundant and structurally conserved neurotransmitter that has been implicated in a number of important physiological functions, including energy homeostasis, stress response, and anxiolysis. In addition to the therapeutic potential of NPY-related drugs in treatment of hypertension, obesity, and depression, there is also evidence that NPY is an important biomarker of neurological health. Therefore, detection and monitoring of NPY levels is of the utmost importance in identifying and diagnosing brain trauma, as well as stress- and anxiety-related disorders, including post-traumatic stress disorder (PTSD).
Many traditional methods for detection of NPY and other biomarkers rely on complex, time consuming, and expensive assays using antibodies. Antibodies raised in various species against NPY often exhibit cross-reactivity when used as sensing elements in microarrays, and the production process is laborious and cost-ineffective. Moreover, antibodies are large, multi-domain proteins with a short shelf-life as a result of protein denaturation, which limits their scope in biosensor development. Other detection methods such as radioimmunoassay (RIA) or enzyme linked immunosorbent assay (ELISA) require trained technicians, specialized equipment, and long analysis times. Therefore, development of alternative detection methods is required for efficient physiological monitoring of NPY levels.
Previously, short oligonucleotide sequences referred to as aptamers have been isolated against NPY and other biomarkers. However, the aptamer selection process suffers from considerable disadvantages. Selection of NPY-binding oligonucleotides is performed in free solution, and aptamers bound to the target NPY are subsequently separated from non-binding oligonucleotides by capillary electrophoresis. In order to achieve effective separation, the injection volume, i.e. the pool of random nucleic acid sequences is rather low. It is important to use as many different sequences as possible in the first selection round to increase the number of potential specific NPY binders, and low injection volume significantly limits the effectiveness of selection. Moreover, negatively charged nucleic acids require counter cations and special buffer systems to be able to fold correctly into their active state, and these requirements generally limit their ability to bind to NPY (pI=5.5).